Propeller



July 14, 193 G. A. AMBJURNSON PROPELLER Filed March 26, 1934 m m m W y M fl V m, w 6

ATTORNEY Patented July 14, 1936 UNITED STATES PATENT OFFICE Application March 26, 1934, Serial No. 717,530

- In Sweden March 29, 1933 7 Claims.

The invention relates to propellers and more particularly to the shaping and disposition of the blades thereof.

The primary object of the invention is the pro- 5 vision of a propeller of this character wherein a higher degree of eiiiciency is attained and a more efl'ective equalization of the rearward thrust and concentration of the force of the propeller.

Further objects and advantages to be attained 10 will more fully appear in the following description: I

The invention is equally applicable to propellers.

of both the marine and aircraft types and it consists essentially in the peculiar characteristics of 15 a propeller having its blades inclined forwardly and uniformly curved in the direction of rotation and said blades having curvilinear cutting and trailing edges, with the working faces of the blades uniformly curved in a-forward direction or in the direction of rotation as hereinafter described and 2 pointed out with particularity in the appended claims In the accompanying drawing forming part of this application and illustrating practical adapta-.

25 tions of the invention Figure l is a fragmentary elevation of a propeller blade of the marine type looking toward the working face thereof.

Figure 2 is a fragmentary vertical sectional view. 30 Figure 3 is an end view looking toward the tip of the blade.

Referring to the drawing in detail, particularly Figures 1 to 3 inclusive, Ill designates the blade of the propeller and II the hub, this carrying the hole for the mounting of the hub in the use of the propeller. The workin'gJace 9f the blade I is comparatively straight along the axial or radial lines a, b and c, respectively, and on a longitudinal line it is uniformly curved forwardly in the direc- 40 tion of rotation on a radius substantially equal to the length of the radius from the axis of the propeller to the peripheral end of the blade. 0. indicates the center from which the circular contour 12 of the tip of the blade is taken, while 0 is 5 the point from which the cutting edge l8 of the blade starts at the hub II and through the radial line b and from which line 1 extends, while 0 identines the angle between the radial line b and the line I, which is approximately thirty degrees.

50 The extreme forward point of the blade in the direction of rotation of the propeller is indicated at 14 this being on the cutting edge and the trail-,- ing edge of the said blade at i5 which point I: at said trailing edge is approximately one-half the 55 length of the radius of the propeller from the center of the hub. h indicates the median be tween the point e and the point i and through which line 7' passes to the point It at the trailing edge l5, while the line 1 extends from the point h to the tip of circular formation [2, the angle bc- 5 tween the points scribed by the arrows 1n being approximately forty-five degrees, which indicates the forward set of the blade in the direction of rotation, while from the points scribed by the arrows 11. is identified the trailing edge angularity which is approximately forty-fivedegrees. Any point of the arc of the curve of the trailing edge i5 intersects any of the axial radii, while the point i of the arc is fixed within the area of the periphery of the hub. The center of the hub l l is 15 indicated at the point 0, while the line p from this center to the forward edge l4 of the said blade is a distance that this edge is forward of the direction of rotation of the propeller, while the lines q and 1' indicate the radius from which the cutting and trailing edges are drawn, respectively, the center for the radii 1' being indicated at sin Figure 2 of the drawing.

The lines t, u, v and w, as indicated in Figure 3 of the drawing, are the zones of the slight curvatures transversely of the blade, the curvatures being identified at :c, y and z in Figure 1 of the drawing. Thus it will be apparent that the blade in has a concaved working face and is of screw form, inclined forwardly and uniformly curved in the direction of rotation of the propeller.

The cutting edges I3 and the trailing edges i5 of said blades are curvilinear and preferably truly arcuate, as will be presently described, and said blades are leaned forwardly in the direction of rotation, or, in other words, the outer or peripheral end portions are somewhat in advance of the inner or central end portions 'of the blade and the curved cutting and trailing edges, respectively, are circular.

The trailing edge ii of theblade is curved on a radius substantially the same as the radius from the axis of the propeller to the end portion II of the blade, the center from which the curve is-struck being located so that the line of said edge l5 beginning at a point substantially tangential to the hub crosses or intersects an imaginary radial line at a point approximately onehalf the length of the latter. This determines the forwardly inclined set of the blade with respect to the direction of rotation thereof. The cutting edge I of the blade is also formed on the same radius as the trailing edge l5 but from I a'diiferent center which is determined by the relative widths of the blade at the inner and outer portions thereof.

In the operation of the propeller constructed and arranged according to the present invention, the forwardly inclined end portion of the words, the displaced fiuid is directed toward the center of the propeller so as to confine the propulsive effort -of the propeller to a minimum area, the fluid being directed into a column revolving about the axis of the propeller and extending longitudinally in the surrounding fluid.

The result of this action is the projection of a restricted column of fluid which tends to contract and taper rather than disseminate or diverge as usually occurs as a result of the operation of the ordinary screw or radial blade propeller.

By the construction and arrangement of the propeller according to the present invention, the longitudinal thrust is equalized over the entire working surface of the propeller and by the resultant concentration of the displaced fluid into a column immediately in rear of the propeller and in axial alignment therewith, the full reactionis available for propelling the ship whether it be of the marine or aircraft type.

While thestructures illustrated in the drawing and described in the foregoing specification disclose practical and preferred adaptations of the invention, it is to be understood that the same admit of considerable modification and alteration within the spirit and scope of the invention as defined by the appended claims. What is claimed is: v 1. A propeller of the character described, comprising ahub portion and blades extending from said hub portion and each having changed pitch on every transverse line of section throughout the length of. the blade, the working face of the blade being uniformly curved forwardly in the direction of rotation, the forward outer end portions of said'blades-being in advance of the forward hub portions thereof, said blades having their cutting and trailing edges respectively curved on a radius equaling the radius from the axis of the propeller to the peripheral'end of the blade, said cutting and trailing edges beginning tangentially to the hub portion 'on opposite' ends thereof and merging roundingly at the peripheral end of the blade.

2. In a propeller, a blade having a trailing edge which is curved on a radius substantially equal to the length of the radius from the axis' tation, one point of the arc of the said curve being. at the point of intersection of any of the axial radii, and theother point of the are be- "ing fixed substantially in the area of the periph- J ery of the usual hub of a propeller. '3. In a propeller, a blade having a"trailing edge which is curved on a radius substantially equal to the length of the radius fjrdrn the axis of the propeller to the peripheral end of the blade, the working face of the blade being uniformly curved forwardly in the direction of roof the usual hub of a propeller, said blade being .of the blade I" said blades being in advance of the forward hub tation, one point of the arc of the said curve being at the point of intersection of any of the axial radii, and the other point of the are being fixed substantially in the area of-the periphery of the usual hub of a propeller, said curve 5 beginning at a point substantially in the area of the periphery of the usual hub of a propeller, so as to intersect the said axial radius to extend to the peripheral end of the-blade.

4. In a propeller, a blade having a trailing l0 edge which is curved on a radius substantially equal to the length of the radius from the axis of the propeller to the peripheral end of the blade, the working face of the blade being uniformly curved forwardly in the direction of rotation, one point of the arc of the said curve being at the point of intersection of any of the axial radii, and the other point of the are being fixed substantially in the area of the periphery of the usual hub of a propeller, said blade having its outer end portion so constructed and arranged as to lead its inner end portion in the direction of rotation.

5. In a propeller, a blade having a trailing edge which is curved on a radius substantially 25 equal to the length of the radius from the axis of the propeller to the peripheral end of the blade, the working face of the blade being uniformly curved forwardly in the direction of rotation, one point of the arc of the said curve 30 being at the point of intersection of any of the axial radii, and the other point of the arc being fixed substantially in the area of the periphery of the usual hub of a propeller, said blade having also a cutting edge formed on the 35 same radius as the trailing edge, one point of the arc of the said cutting edge being substantially in the area of the said periphery, but being on the opposite end of the axis to the other point in the area of the said periphery, the other point of the arc of the cutting edge being struck from a different center to that of the trailing edge, depending upon the desired width of the of the propeller to the peripheral end of the blade, the working face of the blade being uniformly curved forwardly in the direction of rotation, one point of the arc of said curve being, at the point of intersection of any of the axial radii, and the other point of the'arc being fixed substantially in the area of the outer periphery set at a predetermined angle longitudinally of the hub throughout the length of the blade from the hub end portion to the peripheral end portion y 7. A propeller of the character described, comprising a hub portion and blades extending from said hub portion at varying angularity on every transverse line of section throughout the length of the blade, the forward outer end portions of portions thereof, said blades having their cutting and trailing edges respectively curved on a radius equaling the radius from the axis of the -s=prope11er tothe peripheral endof the blade, said cutting and trailing edgesrbe'ginning tangentially to the hub portion on opposite ends thereof and :merging roundinglyat the peripheral end of the blade.

GUSTAV ADOLF AMBJoRNsoN. 

